There are known various types of compressors for air conditioners, e.g. a type shown in FIG. 10 in which a piston 3 is reciprocated by a plate 2 having both sides inclined obliquely and fixed to an input rotary shaft 1, a type shown in FIG. 11 in which a piston 7 is reciprocated through a rod 6 by a plate 5 having one side inclined obliquely and fixed to an input rotary shaft 4, and a variable-capacity type as shown in FIG. 12 wherein a piston 11 is reciprocated through a rod 10 by an inclined plate 9 secured to an input rotary shaft 8 at an adjustable angle. Any of these types is provided at its rotary portion with roller bearings.
More specifically, in case of the type shown in FIG. 10, needle roller bearings 21 having a cage and thrust needle bearings 22 are used. The type shown in FIG. 11 uses shell type needle roller bearings 25 and thrust needle bearings 22 and the variable-capacity type shown in FIG. 12 uses needle roller bearings 21 having a cage and thrust needle bearings 22.
Such compressors used in an air conditioner contain a mixture of lubricant for bearings and refrigerant. The lubricant is repeatedly liquefied and vaporized due to compression and expansion by the compressor. Such lubricant is put under harsher conditions than ordinary hydraulic oils.
As described, bearings used in a compressor for an air conditioner are in a poor lubricating condition since the refrigerant tends to mix into lubricant and the amount of lubricant tends to decrease. This will cause peeling damage on the polling surfaces, which may lead to premature peeling.